Characteristics of distance education interventions and related outcomes in primary school children during COVID-19 pandemic: A systematic review

The COVID-19 pandemic containment measures such as school closures remarkably disrupt the educational system, from in-person learning to remote or distance education with different interventions. This study aimed to identify the characteristics of interventions in remote or distance education during the COVID-19 pandemic and evaluate the outcomes of each intervention. A systematic review was conducted between October 2021 and May 2022 using four databases. Finally, 22 studies met the eligibility criteria and were included for data analysis. Most of the interventions were synchronous student-centered approaches followed by asynchronous student-centered approaches and mixed-learning through online channels such as desktop- and web-based modality. Remote or distance education is effective in academic development in any learning approach while having mixed effects in student attitudes and perceptions. Academic-related behaviors were most engaged by students in synchronous student-centered approaches. Finally, difficulties or burdens, and mental health or social interaction were similar for all learning approaches in technological problems and support systems from families and teachers. Synchronous student-centered approaches should be the main method of education, but other approaches can be used to complement based on the students’ needs. Finally, educational infrastructure and support from teachers and parents are also necessary in remote or distance education. Further studies are needed to focus on primary school students, especially in low-income regions, and apply a randomized study design.


Introduction
The novel coronavirus  was recognized as a global pandemic by the World Health Organization [WHO] and governments in each country including Thailand have implemented several measures to prevent transmission such as travel restrictions and closure of public spaces including school closure [1,2]. Despite being an effective preventive measure, school closures did not only impact students' health, but they also affected children's learning for both short and long term [3]. School closure policies have been partially and fully implemented by many countries for more than 40 weeks since February 2020 [3]. It was found that about 90 percent of 188 countries had adopted online and/or broadcast remote learning policies [4] called 'Emergency Remote Education', which is an unplanned transition from traditional learning and teaching methods to remote ones in a state of emergency [5]. It can be adapted in online and offline platforms, with different pedological approaches and communication synchronicity [6]. Evidence has shown that COVID-19 and its policy responses have significant impacts on global education due to school closures and teaching transformations for long periods of time during the pandemic [4]. A systematic review of online learning during COVID-19 between 2019 and 2020 by Mohtar and Yunus [2022] addressed that only half of the findings [40 studies] revealed that students has engaged with online learning [7]. Accordingly, the academic performance of children has been negatively affected due to lack of contact hours and consultations with teachers when facing difficulties in learning/understanding [8]. Furthermore, children in poorer households that lack internet access, personal computers, television, or radio at home face learning inequalities [9]. For mental health, it was found that there was an increase of anxiety and loneliness in young children alongside child stress, sadness, frustration, indiscipline, and hyperactivity [10]. Overall, school closure policies with remote or distance education have different outcomes on learning engagement, academic achievement, access to educational resources, and mental well-being.
Although there are several advantages to remote or distance education, such as time and money savings and flexibility in learning methods, there are some challenges, such as a lack of communication and social interaction and complicated educational technology [11]. Accordingly, it emphasizes the urgency of remote or distance education's impact evaluation during the COVID-19 pandemic, which tends to be unprepared. Moreover, remote or distance education is more likely to be an option integrating with in person learning even the COVID-19 pandemic disappears. Compared to other levels of education, the implementation of emergency remote or distance education is more challenging for primary school students, aged 6-12 years old. This is because they are still developing their self-regulation and attention control skills and are relatively technologically incompetent compared to students in secondary and tertiary education [11]. Previous systematic review studies by Bond [2021] and Crompton et al. [2021] about remote or distance education during COVID-19 specifically focused on secondary school students as the target population and mostly conducted in high-income countries [6,12]. It also aimed to describe the technology used during the COVID-19 pandemic which was internet-based [6] and the tool typology were synchronous collaboration tools, knowledge organization and sharing tools, text-based tools, multimodal production tools, and social networking tools [6,12]. Although the educational outcomes were systematically reviewed covering effects on academic performance, student engagement and educational inequality [13], the information of different distance educational interventions and its outcomes was sparse. Therefore, this study aims to identify the characteristics of interventions in remote or distance education during the COVID-19 pandemic and evaluate the outcomes of each intervention on socioemotional and behavioral changes, attitudes or perceptions, difficulties or burdens, and academic achievement among primary school children.
studies, assessing quality and extracting data. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] [14], see S1 File.

Operational definitions
The pedagogical approach includes teaching methods consisting of teacher-and student-centered approaches [15]. The teacher-centered approach involves the teacher playing the role of a master of a subject with little or no involvement from learners while the student-centered approach was the method that instructors play role as both teachers and learners [15]. Communication synchronicity is determined by the time of learning between teachers and learners; the synchronous approach occurs when teachers and learners are engaging at the same time whereas the asynchronous approach occurs at different times [16]. These definitions were applied to thematize data in different types of educational intervention linking with its outcomes in the data analysis part.

Search strategy
The search terms were developed in three domains: a] COVID-19; b] primary education; and c] remote or distance education with exclusion of higher education, adult learning, health professional education, special education for children with disability, and physical health [see the details of each search term in Table 1]. These were applied in four databases: PubMed, Scopus, Web of Science, and EBSCOHOST due to the database's coverage in public health and education. The limitation of English literature, journal article and timeline from 2020 to 2021 will be used.

Eligibility criteria
Inclusion and exclusion criteria were applied to ensure article relevance to the study objectives by using the PICO strategy as shown in Table 2. The inclusion criteria comprised of studies that involved children aged 6 to 12 years or are in primary schools, remote or distance education during a public health emergency, and intervention outcomes such as socioemotional and behavioral changes. The documents included in this study were peer-reviewed literature from primary research, published in English language between 2020 and 2021 [COVID-19 pandemic period], and with retrievable full-text articles. The studies related to higher education, adult learning, health professional education, special education for children with disability,

Domains
Search terms COVID-19 covid* OR corona* OR "SAR-Cov*" OR CoV* OR "2019-nCoV" OR "n-CoV" AND Primary education "elementary school" OR "middle primary" OR "upper primary" OR "primary school" OR student* OR pupil* OR child* OR kid* AND Remote or distance education "distance education" OR "distance learning" OR "online education" OR "online learning" OR "remote learning" OR "remote education" OR "remote schooling" OR "virtual learning" OR "virtual education" NOT universit* OR "higher education" OR postgrad* OR undergrad* OR "tertiary education" OR college OR campus* OR dent* OR nurs* OR pharmac* OR medic* OR "health professional*" OR "health worker*" OR "healthcare worker*" OR "health personnel" OR clinic* OR patient* OR disabilit* OR physical activit* OR nutrition OR diet* https://doi.org/10.1371/journal.pone.0286674.t001

PLOS ONE
and physical health outcomes were excluded as same as grey literature and articles in other languages. Empirical studies were included covering quantitative and qualitative studies which would be reflecting the objective and subjective educational outcomes.

Study selection
Six researchers [HK, MP, SU, WK, SJ, PS] were responsible for title, abstract and full-text screening, and quality assessment. Groups of two or three researchers independently screened titles and abstracts first; if there was a disagreement among them, they would discuss to reach a consensus. The same process was conducted for the quality assessment and full paper review.

Data analysis
Data analysis had two parts: quality assessment and data extraction. Independent data analysis was individually undertaken by researchers. If there was a disagreement or unclear information, a consensus would be reached among researchers to ensure data accuracy. Quality assessment. The Joanna Briggs Institute [JBI] critical appraisal tools were used to assess quality of each full-text article [17]. This appraisal covered the ethical consideration and possibility of bias in data collection such as inclusion and exclusion criteria and loss to follow up, data measurement and data analysis [17]. According to different study designs, such as quasi-experimental study and cross-sectional study, the quality of each study type was separately assessed following the JBI critical appraisal tools. Although the JBI tool was developed to assess study in qualitative aspects, the quality score in percentage was also applied to evaluate overall quality and the cut-off point of acceptable quality was set at more than 50% [18].
Data extraction. Data related with these three themes was analyzed including: a] characteristics of studies-author, title, year of publication, objective of study, country, study design,  [16], and intervention delivery modes [desktop-based/webbased/TV-based/radio-based/paper-based modality] [19]; and c] intervention outcomessocioemotional and behavioral changes such as mental health, social interaction, or academicrelated behaviors, attitudes or perceptions, difficulties or burdens, and academic achievement. Data were tabulated to compare between each intervention characteristics such as teacher-centered and student-centered approach with and without synchronicity. All variables were analyzed in frequency and outcomes would be evaluated into positive, negative and mixed effects [qualitative approach] if there was a mix of statistical analyses used in each outcome. The missing results were not evaluated due to qualitative analysis of this review.

Ethical considerations
The study was approved by the Institute

Results
There was a total of 4,092 articles obtained from the four selected databases from which 1,418 duplications were removed, see Fig 1. During the screening process, 2,352 records were removed due to irrelevance and 14 records could not be retrieved in full text. Three hundred and eight full-text records were reviewed for eligibility, and some were excluded owing to the different or unidentifiable target groups and having no intervention details and outcomes in total of 285 articles. Finally, 22 studies met the eligibility criteria and were included for data analysis.

Study characteristics
The characteristics of study covered study setting, type of study, target population, data collection and data analysis.
The majority of included studies [n = 11] were from Europe followed by Asian countries [n = 8], see Table 3. The remaining studies were scattered across different countries in American and Middle-Eastern regions. About two-thirds of the articles were interventional studies [n = 15] and all of them were quasi-experimental studies. Seven studies were non-interventional or observational studies consisting of observation analytic study [cross-sectional study] [n = 5] and descriptive study [qualitative] [n = 2]. The target groups of 11 studies were specifically primary school children in grade 4 to 6 or children aged around 10 to 12 years old, while participants in other included studies were mixed across early and late elementary school levels [n = 8] and only three studies related specifically to children in grades 1 to 3.
All the studies included applied non-randomization sampling, for example, convenience or purposive sampling for quasi-experimental and descriptive studies. For the cross-sectional studies, a mix of sampling techniques were used. Data measurement depended on study outcomes of interest, but most of the quantitative studies employed survey questionnaires as measurement tools, and the qualitative studies generally used semi-structured interviews. Data analysis methods depended on the objectives of each study; for example, the studies that aimed to identify association between variables applied Pearson's and Spearman's correlation analysis or t-test and ANOVA test of pre-and post-test analysis with and without control group for causal relationship evaluation.

Intervention characteristics
A wide range of intervention periods was observed among the nine interventional studies, ranging from five days to five months [see Table 4]. Fifteen studies focused only on studentcentered learning, five studies contained a combination of student-centered and teacher-centered approaches, and two studies utilized the teacher-centered method only. Communication between the teacher and pupils was grouped into three categories: synchronous [n = 9], asynchronous [n = 7], and a combination between the two [n = 6]. Desktop-based [n = 9] and webbased modalities [n = 7] were the most popular interventions, followed by a mixed modality [n = 5] and radio or paper-based modalities [n = 1].
In summary, the characteristics of remote or distance education were classified into a synchronously student-centered approach [n = 9], an asynchronously student-centered approach [n = 6], mixed approaches between student-centered and teacher-centered approaches regardless of synchronicity [n = 7], and a synchronously or asynchronously teacher-centered approach [n = 1], respectively. Examples of the synchronously student-centered approach  (Continued) consisted of exercises or discussions where students received real-time feedback through Snappet and Google classroom [30,41]. The asynchronously student-centered approach was presented via gamification or exercises where students were given flexible learning times such as the Science Level Up program [32]. On the other hand, examples of synchronously and asynchronously teacher-centered approaches comprised lessons that were taught via live video, recorded video, or radio broadcasting [23,38].

Intervention outcomes
Several outcomes of interventions supporting remote or distance education among primary school children during the COVID-19 pandemic were assessed in terms of attitudes/perceptions [n = 13], academic performance [n = 12], academic-related behaviors [n = 11], difficulties/burdens [n = 6], and mental health/social interaction [n = 5]. Each study has one or more than one of these respective assessments.
Positive effects on academic performance were found in any educational type of intervention compared to those who did not receive interventions or before exposure to interventions. Academic-related behavior outcomes such as engagement or motivation had positive effects in synchronously student-centered interventions [20,25,30,41], while other interventions produced a mix of positive and negative results. Difficulties with remote or distance education in all studies were mostly associated with technical issues such as screens freezing or the inability of the school's infrastructure to support the platform's operations [22,23,26,27]. On the other hand, different attitudes or perceptions toward remote or distance education was seen across all intervention types depending on the individual student; for example, some students felt bored and concerned while others perceived enjoyment [29,36]. A similar situation was found for mental health or social interaction where students appreciated the opportunity to interact families, friends, and teachers but also required a support system from parents and teachers to do so [23,24,37,38].

Quality assessment
The JBI critical appraisal tools for analytical quasi-experimental studies [n = 15], cross-sectional studies [n = 5], and qualitative studies [n = 2] were applied to all included articles. Results are shown in a S1 File.
Most of the studies had an overall quality assessment score of higher than 50% [n = 19]; only three studies had a score of lower than 50% and all of them were cross-sectional studies. Among the cross-sectional studies [n = 5], most did not address confounding bias or apply strategies to deal with confounders [33,[36][37][38][39]. In addition, some studies did not clearly define inclusion and exclusion criteria and settings as well as valid and reliable measurements of exposure; however, these defined valid and reliable measurements of outcomes and appropriate analytical methods [36,38,40]. Among fifteen quasi-experimental studies, almost all studies clearly mentioned cause-and-effect variables, similarity between comparisons, exposure of similar treatment between comparisons, outcomes of comparisons measured in the same way, and appropriate data analysis methods. Nevertheless, various limitations among some studies were seen such as comparisons with the control group, evaluation of pre-and post-exposure, complete follow-up, and reliable outcome measurements.

Discussions
The discussion of this study aligned with the results, which were classified into four parts: study characteristics, intervention characteristics, intervention outcomes, and study limitations and recommendations.

Study characteristics
This review shows that the included studies were conducted in diverse regions and countries including both high-and middle-income countries. A previous systematic review of emergency remote education for K-12 by Crompton et al. [2021] noted that the COVID-19 pandemic was different from other emergency situations because it had a global reach and significantly impacted low-income countries [6]. Accordingly, further research in other lowincome regions such as the Middle East, South Asia, South-East Asia and African is needed.
We find that the target group of most remote or distance education studies is less likely to be elementary school students. In this study, the majority of participants included were late primary school students. Therefore, the findings highlight gaps in which further research is needed especially among young children during early primary school year. This will help determine how significant the impact of remote or distance education is on the development of learning and skills as younger students require in-person learning the most [42].

Intervention characteristics
There are various pedagogical approaches to remote or distance intervention in the included literature. The most popular method is synchronous learning, followed by blended synchronicity. A study by Meeter [2021] and Yen and Mohamad [2021] showed that the synchronous student-centered interventions were mostly in the form of exercises or discussions where students received real-time feedback [30,41]. According to Media Naturalness Theory, the level of synchronicity and social communication cues such as facial expression or body language determine the naturalness of media [43]. Therefore, the more synchronous and natural the learning methods, the more preferable they are. It is similar to the result of a study by Seraj et al. [2022], which found that although teachers are in favor of synchronous methods [44], a combination of synchronous and asynchronous methods is also addressed as an optimal approach for teachers' and students' flexibility [45]. Both methods have their own benefits and challenges, so they can be selected based on the different contexts and preferences of teachers and learners.
Online and multimodal learning strategies are preferable by many countries for national distance education policies. According to a study conducted by the Global Education and Technology Team, Education Global Practice, World Bank Group, the policy of remote learning preferred multimodal delivery systems over unimodal delivery systems [46]. They suggested that it is effective to increase coverage, but a clear communication strategy is needed to respond to the local needs and contexts [46]. Accordingly, the multimodal delivery system should be supported to ensure accessibility based on technology capacity and learning preferences.

Intervention outcomes
For the outcomes of distance education interventions, academic performance was not affected by remote or distance education in any educational approaches, which means that remote or distance education is just as effective in terms of academic development as in-person learning. A study by Meeter [2021] among 53,656 students in 2 nd to 6 th grade from Netherlands showed that the average of learning achievement was stronger during the lockdown year compared to the year before, and it remained even the lockdown ended [30]. This idea is supported by a systematic review about the effectiveness of distance learning before the COVID-19 pandemic, which showed that distance education is as effective as faceto-face learning in terms of student learning outcomes [74% of literature in the systematic review] [47]. Although a meta-analysis study by Ulum [2022] revealed that online education during the COVID-19 pandemic had moderate effects on academic performance compared to traditional learning, it has not been influenced by different online education approaches [48]. Therefore, in terms of academic outcomes, any pedagogical approaches and synchronicity in remote or distance education can be applied during public a health emergency.
Academic-related behavior outcomes, attitudes, and perceptions are determined by various learning approaches. The synchronously student-centered interventions are more engaging compared to other types. A study by Yen and Mohamad [2021] addressed that the use of Google Classroom revealed an increase in motivation among users in mastering spelling from the perspective of active participation and teamwork [41]. Compared to a study by Christopoulos and Sprangers [2021] about asynchronously student-centered approach that some students appreciated the intervention and wanted to keep practicing, whereas others felt frustration and dissatisfaction [22]. According to a study by Aguilar et al. [2022], there is a substantial association between live instruction and student engagement in online learning among primary school pupils in California [49], making synchronized student-centered interventions more engaging than other types. There was a 26% increase in the likelihood that students will finish all of their assignments for every additional hour of live instruction per week [49]. Student engagement can be explained by self-determination theory consisting of autonomy [feel in control of our own behaviors and goal], competence [feel competent and effective], and relatedness [experience interaction and feel connected] [50]. A synchronously student-centered approach can easily achieve these factors, especially for relatedness and competence, while an asynchronous approach encourages autonomy. Therefore, different learning approaches may not fully determine academic-related behavior outcomes but addressing each student's selfdetermination and personal preferences are more important.
Remote and distance education intervention success depends on organizational factors such as technology infrastructure readiness, personal factors such as familiarity with technology and family support, and pedagogical factors such as course design and course delivery [51]. All these factors are addressed by the included studies in this review and there are similar views towards difficulties and burdens, and mental health or social interaction. Students mostly complained about technological problems and requested for support from families and teachers. It is similar to qualitative studies from parents and educators about the impact of remote learning on primary students' well-being in that it has both positive and negative effects determined by supports from teachers, parents, and schools [52]. This emphasizes the importance of technology infrastructure preparation and a solid support system for learners.

Quality assessment
Most of the study are quasi-experimental study and there are various limitations in comparisons with the control group, evaluation of pre-and post-exposure, complete follow-up, and reliable outcome measurements. A study by Huertas-Abril [2021] showed limitations in comparisons with the control group or pre-and post-exposure evaluation, and incomplete followup [26]. Quasi-experimental study is a manipulation of intervention to study group with nonequivalent control and quasi-independent variables [53]. Quasi-experimental study needs control or comparison group which can be one group design of pretest and posttest or non-equivalent control design [53]. According to experimental design, the follow up data is necessary to interpret the results, so it is necessary to have strategy dealing with incomplete follow-up or selection bias such as describing characteristics of loss follow-up group [54]. Thus, future research should reduce these biases to improve research quality in this field.
This review is a novel study that aims to systematically evaluate the outcomes of specific types of distance education interventions in primary school students who are significantly affected by education disruption compared to students at the secondary and tertiary levels. Nevertheless, this study also has several limitations. Firstly, there were multiple quasi-experimental studies in this review. Although this type of study can evaluate the causal relationship between intervention causes and effects, the issue of selection bias remains compared to randomized controlled trial studies [55,56]. Furthermore, future quasi-experimental studies should concentrate on control group comparison and loss follow-up strategies. Secondly, as all studies were conducted during the COVID-19 pandemic, and it seemed difficult to collect the data for pre-tests, or to find appropriate control groups in the quasi-experimental studies. Therefore, continuous data monitoring on repeated measurements or a time series analysis will be of great value to better understand changes for the further program's implementation. Lastly, the databases used may not have covered databases specific to the educational field since this might lead to selection bias. Future research should focus more on randomized study designs or should implement control groups for evaluation study and expanding database coverage for systematic review.
This study recommends that remote or distance education can be an alternative in primary school education to maintain academic performance during the crisis situation. Synchronously student-centered interventions are supposed to be promoted due to academic engagement. However, the technology infrastructure and support system from teachers and families should be considered by school administrators and policy makers to ensure effective remote or distance education.

Conclusion
School closures due to the COVID-19 pandemic significantly disrupted the educational system and required the transition from in-person learning to remote or distance education. Consequently, different educational interventions were applied in various settings. In this study, the outcomes of each intervention were explored in primary school students. Most of the interventions were synchronously student-centered approaches utilizing online channels. In evaluating academic performance, remote or distance education was found to be effective in terms of academic development by using any learning approach, but the findings on attitudes and perceptions were mixed between positive and negative views. Positive academic-related behaviors were also seen when using a synchronously student-centered approach [e.g., positive outcomes in engagement]. Finally, difficulties or burdens, and mental health or social interaction reported similar results for all learning approaches. These included technological problems and support systems from families and teachers. While a synchronously student-centered method is recommended as the main intervention due to its excellent outcomes for academic achievement and engagement in academic behavior, other approaches can also be used in conjunction if it addresses students' needs. Finally, the educational technology infrastructure and support system from teachers and parents are also necessary in remote or distance education. Future studies should further explore intervention outcomes on primary school students, especially in low-income regions, with a randomized study design.
Supporting information S1 File. The JBI appraisal checklist of quasi-experimental, cross-sectional, cohort and qualitative studies. The protocol, template data collection forms, and data extracted from included studies were not publicly available and had not been registered. (DOCX) S2 File. (DOCX)